[WIP] fix: model config parity between python and go

[supreme-gg-gg]

Do not merge, still need more testing with Ollama and Bedrock

Summary

Closes most of the gap between python and go identified in #1643

• TLS and api key passthrough for LLM provider
• Support Ollama and Bedrock using client SDK as we've done earlier in feat(kagent-adk): remove litellm as dependency from kagent-adk #1540
• Refactor embedding models in python to be separate from memory service

This will allow most users to directly switch from runtime: python to runtime: go without needing to worry about existing LLM provider configs since everything will be supported on the Go side, improving adoption of the new go runtime

Testing Plan

• All new unit tests in go adk passes, all old unit tests in python passes
• Bedrock LLM and embedding model in Go runtime
• Ollama LLM and embedding model in Go runtime
• Gemini / OpenAI with TLS / Api key passthrough in Go runtime